Process and device for stabilizing electric arcs



arch 18 1924., 1,486,990

W. SIEBERT PROCESS AND DEVICE FOR STABILIZING ELECTRIC ARCS Filed May 13. 1922 3 gm ill 5 2 51 55111 i q 2 1 flfic y 8 t \I: 8 f/ T323 57 \I ,1

ZRMQZZZOW Patented Mar. 18, 1924.

UNITED STATES PATENT orn-ca.

WERNER SIEBERT, 0F LAUIENBURG, SWITZERLAND, ASSIGNOR TO NI'IBUM AKTIEN- GESELLSCHAFT, 0F ZURICH, SWITZERLAND, A CORPORATION OF SWITZERLAND.

PROCESS AND DEVICE FOR STABILIZING ELECTRIC Application filed m 13, 1922. Serial No. 580,726.

To all whom it may concern:

Be it known that I, Dr. WERNER SIEBERT, a citizen of the Republic of Germany, residing at Laufenburg, Aargau, Switzerland, have invented certain new and useful Improvements in Processes and Devices for Stabilizing Electric Arcs, of which the following is a specification, reference being had therein to the accompanying drawing.

The invention has reference to a process and a device for stabilizing electric arcs in electric furnaces. In many electric furnaces and particularly in furnaces used for oxydizing atmos heric nitro en, large electric arcs are emp oyed, the e ectrodes being at such a distance from each other that a restoration of the arc does not take place automatically if the arc has accidentally been interrupted. Such is the case for example in the furnace described in the U. S. Patent No. 1,033,126. Each time the arc is interrupted, it must be restored which is more or legs1 diflicult according to the system emloy p Now it has been found that sudden extinctions of such arcs can be avoided or reduced to a minimum by placing a substance in the neighbourhood 'of the are, which can be brought to a high temperature, so as to ionize the circulating gases. Possibly not only ionization but also a slight evaporation of the heated substance takes place which increases the conductivity of the .gases. It was not possible to foresee that this effect could beT btained with ordinary bricks of fireproof material or magnesite bricks or with any other refractory substance. However the xesult has been at-' tained that the proper choice and the application of fire-proof or other bricks allow such furnaces to work constantly during several days without the arc bein extinguished which is, in any case. a considerable improvement. The fire-proof material itself is affected only to a very small extent and lasts for a considerable time without having to be replaced.

An example of the application of this invention is diagrammatically-illustrated in the accompanying drawing, showing a section through a furnace.

In the brick lined furnace 1 an arc 6 as described in the U. S. Patent No. 1,033,126 is shown between the electrodes 2, the distance between the electrodes measuring from 2 to 3 meters with a furnace load of several thousand kilowatts. The air is introduced into the furnace through nozzles 7 -distributed over the inner periphery of the furnace, placed at an acute angle thereto and connected to the air supply ipe 3. The air forced into'the furnace produces a violent whirl, whereby the arc is spread horizontally into a disc-shaped flame. The air passes the arc and the nitric oxides formed therebyleave the furnace at4. In operating a furnace of this type it has been found that the arc extinguishes often which is not only very annoying but means also a reduction of output.

The extinction of the arc can be avoided by erecting one or several columns 5 consisting of fireproof material at the places indicated on the drawing or in the neighbourhood of the places shown, the tops of-these columns reaching the zone of the hot gases. The exact place of the columns is indifferent but it is important 'to place them so that they are sufliciently heated by the arc.

The columns 5 consist preferably of blocks of highly refractory material. [The so-called basic stones as well as acid stones may be used, such as aluminium-calciumsilicates having anexcess ofsilicic acid or of aluminic oxide. The chemical composition of the stones must be such that the melt ing point is not below 1200-1400 C. so that they do not become liquefied or sinter at the temperature of the furnace. Blocks of magnesium oxide may also be used.

In a way similar to that given :in the drawing the same stabilizing effect on arcs of furnaces of other constructions can be attained. a

. I claim:

1. The stabilization of electric arcs in electric furnaces by introducing refractory substances into the zone of the electric arc.

2. The stabilization of electric arcs in electric furnaces, by heating refractory substances placed within the reach of the electric are by the arc itself, thereby increasing the conductivity of the gases passing the electrodes.

3. In an electric furnace the combination 5 with electrodes normally arranged in a horizontal plane of refractory material placedfi in such a position that the are formed between the electrodes heats the refractory material and thereby increases the conducticity of the gases passing the electrodes and 10 stabilizes the arc.

In testimony whereof I aifix my signature.

DR. WERNER SIEBERT. 

